Several techniques have been used in the past to solve structural problems caused when buildings are built on expansive soils which shrink and swell with moisture. Specifically, below-grade barriers can be installed after construction and after distress manifests itself in a building. These after the fact barriers are very expensive and intrusive. Moreover, these barriers are placed several feet beyond the existing building slab or footing thereby necessitating an additional barrier to prevent moisture from migrating between the below-grade barrier and the existing building slab or footing. Repairs after the fact are extremely costly depending on the amount of damage associated with the foundation movement due to the expansive soil below. Other similar barriers used to repair damage after the fact include cutoff walls of concrete or synthetic membranes.
The use of after the fact remedial approaches to repair damages to structures caused by expansive soils is more costly and time consuming than installing a vertical wall to prevent moisture seepage at the time of initial construction. With after the fact remedial procedures, landscaping is destroyed, mechanical units are relocated, patios and driveways are torn up, and owners and occupants of the property are displaced for weeks at a time to allow time for the repairs.
In the prior art methods, post-tensioned concrete slabs have been used to deal with expansive soils. This type of construction, however, is expensive and requires extensive engineering and specialized construction techniques. Additionally, the floor plan designs are limited due to the constraints inherent in post-tensioned slabs. The current invention eliminates these constraints, is simple to install and will prevent the distress in buildings caused by foundation movement associated with both expansive and collapsible soils. Therefore, it is desirable to have a vertical wall that extends into the soil and is integral with the building foundation in order to prevent moisture from migrating into the zone of influence under the building foundation.
Various techniques have been disclosed in U.S. Pat. No. 4,015,432 (H F Ball), U.S. Pat. No. 4,534,143 (Goines et al.), U.S. Pat. No. 5,924,251 (Jalla), U.S. Pat. No. 4,508,472 (Handy), U.S. Pat. No. 3,269,126 (Freeman), U.S. Pat. No. 1,746,918 (Webster), U.S. Pat. No. 7,131,239 (Williams), U.S. Pat. No. 7,003,918 (Williams), U.S. Patent Application Nos. 20080304919 (Coyle), 20030233798 (Berkey et al.), 20030188496 (Williams), and International Publication No. WO 2005021874 (Bashford) to overcome the problems with building on expansive soils. However, these disclosures suffer from one or more of the following disadvantages. First, none of these inventions include a vertical wall that extends deep below the surface of the soil and is integral with the building foundation. Second, none of these inventions are simple and inexpensive designs. Third, most of the inventions above are remedial in nature rather than including a design that prevents foundation problems at the time of initial construction.